Upregulation of CC Chemokine Receptor 7 (CCR7) Enables Migration of Xenogeneic Human Adipose-Derived Mesenchymal Stem Cells to Rat Secondary Lymphoid Organs.

BACKGROUND CC chemokine receptor 7 (CCR7) expression is vital for cell migration to secondary lymphoid organs (SLOs). Our previous work showed that inducing CCR7 expression enabled syngeneic mesenchymal stem cells (MSCs) to migrate into SLOs, resulting in enhanced immunosuppressive performance in mice. Given that human adipose-derived stem cells (hASCs) are widely used in clinical therapy, we further investigated whether upregulation of CCR7 enables xenogeneic hASCs to migrate to rat SLOs. MATERIAL AND METHODS hASCs rarely express CCR7; therefore, hASCs were transfected with lentivirus encoding rat CCR7 (rCCR7) plus green fluorescence protein (GFP) or GFP alone. CCR7 mRNA and cell surface expression of rCCR7-hASCs and GFP-hASCs were examined by reverse transcription-polymerase chain reaction (RT-PCR) and flow cytometry (FCM), respectively. The phenotype, differentiation, and proliferation capacity of each cell type was also determined. To examine migration, rCCR7-hASCs and GFP-hASCs were injected intravenously into Lewis rats, and the proportion of GFP-positive cells in the spleen and lymph nodes was determined with FCM. RESULTS mRNA and cell surface protein expression of CCR7 was essentially undetectable in hASCs and GFP-ASCs; however, CCR7 was highly expressed in rCCR7-ASCs. rCCR7-hASCs, GFP-hASCs, and hASCs shared a similar immunophenotype, and maintained the ability of multilineage differentiation and proliferation. In addition, the average proportion of GFP-positive cells was significantly higher following transplantation of rCCR7-hASCs compared with GFP-hASCs (p<0.01). CONCLUSIONS These results suggest that upregulation of rat CCR7 expression does not change the phenotype, differentiation, or proliferation capacity of hASCs, but does enable efficient migration of hASCs to rat SLOs.

[Application of computational fluid dynamics in hemodynamic research of aortic arch].

OBJECTIVE: To evaluate the application of computational fluid dynamics (CFD) on a patient-specific hemodynamic model of aortic arch. METHODS: The original Dicom format image data of a patient were acquired by computed tomographic angiography (CTA). A 3-dimensional (3D) model based on CFD was constructed through the right amount of boundary conditions and hemodynamic parameters related with flow velocity, shear force and wall stress on lumen were analyzed accordingly. RESULTS: The 3D model based on CFD could reflect the characteristic of flow velocity, shear force and wall stress on lumen in vitro. (1) The distributions of hemodynamic variables during cardiac cycle were spatiotemporally different. The unidirectional high-speed systolic current was replaced by diastolic eddy current and reversed flow. The distribution of flow velocity and shear stress gradually increased from outer wall of aortic artery to inner wall under the influences of such anatomical factors as vascular branching and distortions of descending aorta; (2) the magnitude and volatility of wall stress in ascending aorta were greater than those of aortic arch and descending aorta, but the least results were at the lateral wall of descending aorta area. In addition, the wall stress of external wall was higher than the lateral wall in the same section. CONCLUSION: The hemodynamic research of aortic arch based on CFD may actually simulate the characteristics of blood flow and wall stress so as to become a new reliable and convenient application tool in etiological diagnosis and surgical planning.

[Hemodynamic study of thoracic aortic aneurysm based on computational fluid dynamics technique].

OBJECTIVE: To establish a patient-specific hemodynamics model of thoracic aortic aneurysm (TAA) based on computational fluid dynamics technique and investigate its role in the study of growth and rupture mechanism of TAA. METHODS: 3D realistic model of thoracic aortic aneurysm was reconstructed from DICOM format computed tomography angiography (CTA) images of a male patient. The geometry was reconstructed using medical image processing software Mimics. The blood flow in aorta was assumed to be laminar and incompressible and the blood Newtonian fluid. A time-dependent pulsatile boundary condition was deployed at inlet. Unsteady blood flow simulation was performed in real geometry of TAA with a finite volume method (FVM) code FLUENT. The hemodynamic parameters related with the growth and rupture of aneurysm were analyzed. RESULTS: Analysis of the distributions of hemodynamic variables during the cardiac cycle such as wall shear stress, streamlines and velocity profiles in TAA were carried out. The numerical simulation results demonstrated that the blood velocity of proximal neck was considerably faster than that of aneurysm body. The outer wall of proximal aneurysm body was hit by blood jet entering aneurysm. Instant streamlines at peak systole showed that the entering blood stream hit the aneurysm wall and right-hand helical vortex was observed in aneurysm body. The distributions of high wall shear stress were observed in the proximal and distal aneurysm neck and the area where the entering blood stream first hit the wall. Large regions of lower wall shear stress occurred in aneurysm body. CONCLUSION: The growth and rupture mechanisms of TAA may be analyzed based on a constructed patient-specific model and hemodynamic simulation.